/*

 * Licensed to the Apache Software Foundation (ASF) under one

 * or more contributor license agreements.  See the NOTICE file

 * distributed with this work for additional information

 * regarding copyright ownership.  The ASF licenses this file

 * to you under the Apache License, Version 2.0 (the

 * "License"); you may not use this file except in compliance

 * with the License.  You may obtain a copy of the License at

 *

 *     http://www.apache.org/licenses/LICENSE-2.0

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 */

package com.bff.gaia.unified.sdk.metrics;



import com.bff.gaia.unified.sdk.annotations.Experimental;

import com.bff.gaia.unified.sdk.annotations.Experimental.Kind;

import com.bff.gaia.unified.sdk.annotations.Internal;

import org.slf4j.Logger;

import org.slf4j.LoggerFactory;



import javax.annotation.Nullable;

import java.io.Closeable;

import java.io.IOException;

import java.util.concurrent.atomic.AtomicBoolean;



/**

 * Manages and provides the metrics container associated with each thread.

 *

 * <p>Users should not interact directly with this class. Instead, use {@link Metrics} and the

 * returned objects to create and modify metrics.

 *

 * <p>The runner should create a {@link MetricsContainer} for each context in which metrics are

 * reported (by step and name) and call {@link #setCurrentContainer} before invoking any code that

 * may update metrics within that step. It should call {@link #setCurrentContainer} again to restore

 * the previous container.

 *

 * <p>Alternatively, the runner can use {@link #scopedMetricsContainer(MetricsContainer)} to set the

 * container for the current thread and get a {@link Closeable} that will restore the previous

 * container when closed.

 */

@Experimental(Kind.METRICS)

@Internal

public class MetricsEnvironment {



  private static final Logger LOG = LoggerFactory.getLogger(MetricsEnvironment.class);



  private static final AtomicBoolean METRICS_SUPPORTED = new AtomicBoolean(false);

  private static final AtomicBoolean REPORTED_MISSING_CONTAINER = new AtomicBoolean(false);



  private static final ThreadLocal<MetricsContainer> CONTAINER_FOR_THREAD = new ThreadLocal<>();



  /**

   * Set the {@link MetricsContainer} for the current thread.

   *

   * @return The previous container for the current thread.

   */

  @Nullable

  public static MetricsContainer setCurrentContainer(@Nullable MetricsContainer container) {

    MetricsContainer previous = CONTAINER_FOR_THREAD.get();

    if (container == null) {

      CONTAINER_FOR_THREAD.remove();

    } else {

      CONTAINER_FOR_THREAD.set(container);

    }

    return previous;

  }



  /** Called by the run to indicate whether metrics reporting is supported. */

  public static void setMetricsSupported(boolean supported) {

    METRICS_SUPPORTED.set(supported);

  }



  /** Indicates whether metrics reporting is supported. */

  public static boolean isMetricsSupported() {

    return METRICS_SUPPORTED.get();

  }



  /**

   * Set the {@link MetricsContainer} for the current thread.

   *

   * @return A {@link Closeable} that will reset the current container to the previous {@link

   *     MetricsContainer} when closed.

   */

  public static Closeable scopedMetricsContainer(MetricsContainer container) {

    return new ScopedContainer(container);

  }



  private static class ScopedContainer implements Closeable {



    @Nullable

	private final MetricsContainer oldContainer;



    private ScopedContainer(MetricsContainer newContainer) {

      this.oldContainer = setCurrentContainer(newContainer);

    }



    @Override

    public void close() throws IOException {

      setCurrentContainer(oldContainer);

    }

  }



  /**

   * Return the {@link MetricsContainer} for the current thread.

   *

   * <p>May return null if metrics are not supported by the current runner or if the current thread

   * is not a work-execution thread. The first time this happens in a given thread it will log a

   * diagnostic message.

   */

  @Nullable

  public static MetricsContainer getCurrentContainer() {

    MetricsContainer container = CONTAINER_FOR_THREAD.get();

    if (container == null && REPORTED_MISSING_CONTAINER.compareAndSet(false, true)) {

      if (METRICS_SUPPORTED.get()) {

        LOG.error(

            "Unable to update metrics on the current thread. "

                + "Most likely caused by using metrics outside the managed work-execution thread.");

      } else {

        LOG.warn("Reporting metrics are not supported in the current execution environment.");

      }

    }

    return container;

  }

}